The present invention relates to the fabrication of carbon nanostructures such as carbon nanowalls and few-layer graphene and, in particular, to an improved process capable of operating at substantially atmospheric pressure and providing oriented nanostructures.
Nanostructures such as carbon nanowalls (CNW) present substantially two-dimensional graphitic platelets of few-layer graphene. It is believed that CNWs may exhibit similar properties to graphene including extremely high ballistic electron mobility, high thermal conductivity, high Young's modulus, and high fracture strength. The large surface area of CNWs holds promise in the fabrication of electrodes for electrical energy storage (e.g. batteries and capacitors), electrodes for solar cells, sensors, and substrates for catalysts. The sharp edges of CNWs may make them useful field emission materials or for generating corona discharge.
Ideally CNWs would be fabricated or arrayed in “vertical” orientation meaning that the substantially planar CNW flakes are extended edgewise perpendicularly from a surface of a substrate to which they are both electrically and mechanically attached.
Current methods of manufacturing CNWs may use a microwave plasma-enhanced chemical vapor deposition (MPECVD) or high current DC plasma enhanced chemical vapor deposition (PECVD) operating in a near vacuum or low-pressure environment (0.1-1330 Pa). The low-pressure environment ensures an adequate mean free path of the electrons promoting sufficiently energetic electrons as is necessary for decomposition of the carbon precursors (such as hydrocarbon gases) providing the feedstock for the CNWs.